tcp: Kill extraneous SPLICE_F_NONBLOCK checks.

In splice TCP receive, the SPLICE_F_NONBLOCK flag is used
to compute the "timeo" value.  So checking it again inside
of the main receive loop to trigger -EAGAIN processing is
entirely unnecessary.

Noticed by Jarek P. and Lennert Buytenhek.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp.c

@@ -597,10 +597,6 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
 					ret = -ENOTCONN;
 				break;
 			}
-			if (flags & SPLICE_F_NONBLOCK) {
-				ret = -EAGAIN;
-				break;
-			}
 			if (!timeo) {
 				ret = -EAGAIN;
 				break;